Oxovanadium(IV) thiocarboxylate paddlewheels containing ancillary Group 10 metals: a comparative study on Pd and Pt derivatives

Vanadyl-containing paddlewheel structures have recently joined the pool of molecular spin systems showing respectable coherence times (Tm). We extended the investigation of [PtVO(SOCR)4] (R = Me, Ph) by synthesizing the corresponding Pd derivatives. Crystals of [PdVO(SOCMe)4] and [PdVO(SOCPh)4]·DCM are isomorphous to their Pt analogues and comprise staggered and square dimers, respectively. For both Group 10 metals, M···M’ contacts in staggered dimers promote a stronger antiferromagnetic coupling than M···S’ contacts in square dimers, with Pd complexes showing a slightly more effective interaction consistent with DFT predictions. In solution, the paddlewheels exist in monomeric form and undergo a quasi-reversible one-electron reduction, more favorable for M = Pd than Pt and for R = Ph than Me. X-band EPR spectra in frozen CD2Cl2/toluene-d8 show the eight-line hyperfine pattern characteristic of 51V (I = 7/2), with identical spin-Hamiltonian parameters across the series. Unlike the interaction with 195Pt (I = 1/2, 34%), the superhyperfine coupling with 105Pd (I = 5/2, 22%) is unresolved. Tm values are essentially the same for Pt and Pd derivatives and follow the same substituent dependence (Ph > Me). Therefore, ancillary Group 10 metal affects redox potentials and, to a lesser extent, solid-state magnetic properties, but leaves quantum coherence unchanged.